Testability is predicted to become a primary design specification and has to be addressed in the early design stages, as escalating test time & costs need to be controlled and quality levels improved. In addition to improved manufacturing tests, Built In Self Test (BIST) offers an extension towards in-field verification while also allowing test re-use and providing a promising approach to automate mixed signal test generation.
Loss of signal detectors are used to monitor a lack of a signal, i.e. when the amplitude of the signal falls below a threshold value and can no longer be detected. Conventional techniques to test a Loss of Signal detector, involve applying test signals below the supposed threshold value at the relevant bond pads of the chip containing the detector circuit. However, using the bond pads to apply the necessary test signals to the Loss of Signal detector is an involved process because it is not easy to inject the required high frequency variable amplitude signals at the bond pads.
There is a need for a simple test method and apparatus for measuring the threshold at which a signal can no longer be detected for a Loss of Signal detector that avoids the drawbacks associated with using bond pads.
There is also a need for a loss of signal test apparatus that can be incorporated onto the chip of the device that it would be used to test, with minimal overhead.
Conventional techniques for determining the hysteresis thresholds of an ACJTAG block involve applying a variable amplitude signal to the relevant bond pads of the chip. Thus there is a need for a non-external test method for determining the hysteresis thresholds of an ACJTAG block.